DE1263196B - Electronically variable delay system - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H03h

German class: 21g-34

Number: 1263 196

File number: W 35148IX d / 21 g

Filing date: August 22, 1963

Opening day: March 14, 1968

The invention relates to an electronically variable delay system having a first and a second delay mediura, with first and second modulators for modulating on of the signal to be delayed to a carrier frequency, the first modulator being connected upstream of the first delay medium and the second to the second, with a device for supplying the signal to be delayed to the first modulator and with a device having an oscillator circuit for supplying a variable carrier frequency to the first modulator.

Ultrasonic delay lines take advantage of the fact that the speed of propagation an ultrasonic wave or an elastic oscillation in general is much smaller than that of electrical signals. The amount of delay available in a delay line depends on the length of the ultrasonic path provided between the input and output transducers, also from the medium used for the ultrasonic path and, last but not least, from the frequency of the ultrasonic waves. A controlled change of the resulting delay time can be done, for example a corresponding influence on the length of the ultrasonic path or the working temperature take place. Such systems are obviously sluggish and imprecise.

A regulation of the delay by changing the ultrasonic frequency depends on the frequency-dispersive Properties of a delay line depend on, is therefore possible if the delay occurs is a function of the frequency of the ultrasonic wave. It has already been suggested to reduce the delay to change that the carrier frequency of the input signal in a suitable point of the delay-frequency characteristic curve of the delay line relocated and then changed in a controlled manner.

However, the delay line not only has different carrier frequencies Dispersion, but also for all frequencies within the bandwidth of a modulated Signal. In effect, a very undesirable phase shift is obtained within the signal band of the signal sidebands. For signals that are in the form of digital pulse trains, one obtains the effect of this dispersion is a pulse broadening that can go so far that the pulses overlap each other.

It is therefore the object of the invention, all frequency components of a broadband high-frequency signal of a uniform, i.e. dispersion-free, non-electronic variable delay system

Applicant;

Western Electric Company,

Incorporated, New York, N.Y. (V. St. A.)

Representative:

Dipl.-Ing. H. Fecht, patent attorney,

6200 Wiesbaden, Hohenlohestr. 21

Named as inventor:

Irvin Ernest Fair, Center Valley, Pa. (V. St. A.)

Claimed priority:
V. St. v. America September 11, 1962
(222788)

Nevertheless, to be able to subject it to a delay that is easily variable in size.

It is known the phase distortion that a high frequency signal in long distance transmission over frequency dispersive transmission media, e.g. B. via waveguides, is subject to correcting that Signal band inverter stations are provided along the waveguide transmission path at certain intervals are. They serve to determine the transmitted signal band, which has a certain frequency dispersion when Passing through the waveguide and through the intermediate amplifier stations that are also provided is subject to inverting and the signal in this form over the next section to the next To transmit amplifier and inverter station. This is the one introduced in the previous section Dispersion gradually disappeared again in the following section. In appropriate Way, this process is along the entire transmission route, which is several thousand miles can be long, repeated to the Erapfangs terminus.

It is general here to effectively amplify and retransmit what is received High frequency signal necessary to reduce the latter first to an intermediate frequency and then again into a high frequency signal at approximately the same frequency as the input high frequency

809 518/548

3 4

to reverse. To do this, the following measures are advisable, the frequency of which is higher - preferably that

required: transmission along a waveguide - twice that of the last-mentioned output

channel, filtering, demodulation, amplification with and with the change in the carrier frequency of the

Intermediate frequencies as well as renewed modulation and the same changes linearly. Amplification at high frequency. 5 So it is that of the first delay medium

When the signal is treated in this way, the supplied signal has an adjustable carrier frequency

a dispersion is introduced when the different are superimposed, so that the time delay in the first

Frequency components of the signal band by each delay medium due to a change in the carrier frequency

different amounts will be delayed. To correct the frequency can be changed. This carrier frequency This signal dispersion must be a delay penalty is then preferably doubled and with the

Zerrer are used, whose dispersion characteristic output signal of the first delay medium is

line opposite to the dispersed present in the signal. Through this second modulation, everyone experiences

sion is. Needless to say, the signal components of the frequency spectrum are an in-

Equalizer characteristic curve only approximately in this sense version with regard to the carrier frequency at the output adapted to the dispersion present in the signal 15 of the first delay medium. When passing through

can be, for this reason is therefore also that of the signal inverted in this way by the second

Equalization only approximate. Delay medium is the overall through the

A known dispersion introduced to compensate for that Freefirst compensates. It will

frequency dispersion, softer the high frequency signal with therefore a controllable overall delay, which is practical Passage through an intermediate amplifier table is equal to the sum of the individual delays,

station is subject, the intended inverter station contains dispersion-free across the entire signal bandwidth

two delay equalizers. One serves as an escape route.

distortion of the intermediate frequency signal and the other. In the following, the invention is based on an in

in addition, the required delay in the sense of an embodiment shown in the drawing Equalization of the high-frequency signal in the same 25 individual described. It shows

respectively. One of the two equalizers F i g. 1 is a block diagram of the embodiment

through an appropriately designed single example and

distortions are avoided, which are the same for all in question F i g. 2 shows a typical delay characteristic in

coming frequencies introduced dispersion cor- depending on the frequency of a disperse ultrarigiert. The amplifier output frequency and the carrier sound delay line.

gereingangsfrequenz be approximately gleichgehal- J _n (j _he Fig. 1 is the source of the signal, the comparable

th, but should be hesitated with the proviso of a small difference, represented by block 11,

in between, so that feedback problems _The signal from this source has the original

be avoided. Message carrying signal, usually

These known arrangements are responsible for what is referred to as the "baseband signal"; and that would be freed from any underlying carrier frequency that it may have been originally introduced over a long-distance transmission path by the transmission medium. To compensate for such a frequency dispersion, so that the signal baseband signal would come to the demodulated side on the receiving side as distortion-free as possible to an amplitude or frequency modulated signal. For this purpose, in principle, signals or a sequence of pulses are used which represent delay elements in the transmission path as digital information. In some cases, the frequency dispersions of which are set against the - it is desirable to delay this signal by a period of time which delay the signal along the transmission path, which is subject to a large area, in opposite directions. A control of an electrical variable of a source 12 of the total delay between transmission and 45 must be changed. A typical application, the receiving side is, has seen to learn this without input _Z ur time great importance to, for Erführung an undesirable frequency dispersion of the importance and usefulness explanation of the impossible. On the other hand, the invention is used. In communications with a dung, as mentioned, the object of an elec- satellite learns the received signal naturally ironic variable image delay system for sheep 50 a considerable delay, owing to the fen in which an always and absolutely zero dispersion _se hr long distances to and from the satellite. Delay in size electronically controlled This delay can be introduced by introducing a. Therefore, for example, the artificial delay would either have some kind of frequency transmission path in the signal coming from the satellite or it would have dispersion in an associated path - regardless of whether this is compensated for. However, since the satellite is growünscht with or not - as the signal should the comparison _he ß speed describes its orbit, changes deceleration system also with the same Frequenzdisper- the distance to a given station to leave sion. the earth, hence the delay. In order to solve this problem, the correct compensation delay in a smooth ironically variable delay system of the initially defined or described type is assumed. The signals obtained electrically according to the invention, which represent the satellite-based solution to this problem, are characterized by movement. Furthermore, if the above records that the first and second dispersion is to be switched to a satellite practically pointing delay medium with regard to their instantaneous delay to another satellite depending on the delay on the frequency of the changing orbit position, tables are identical and: that the second modulator ". the compensation delay also has practically no mixer to mix the output of the first table momentarily from one value to a delay medium with: a second signal to a very different second value.

5 6

Similar requirements arise with electronic correct electrode feeding. Other oscillator telephone exchanges on, furthermore in systems in which a capacitive diode or for converting signals of a television standard a reactance tube in one way or another

be used in another and in numerous military resonance circuit of the oscillator,

Systems that are previously unsatisfactory mechanically 5 are known. By changing the to the diode or

variable delay systems used. Therefore, the voltage applied to the reactance tube becomes its

the sources 11 and 12 are only representative of the capacitance or its reactance changed and thus

Baseband signal or delay control signal also the oscillator frequency. With such a

sources, the nature and structure of which in detail from the circle, the source 12 would be the variable bias voltage

sen or other areas of application. io deliver. It should be noted that other important applications

The delay media 13, 14 are substantially identical for all including the use of the system of a preferred embodiment of the invention in test facilities of the invention, and each may include laboratories manually setting / ₍ any of the various known delays. At this end, the source would contain 16 types of medium in order to have a delay, 15 a resonance circuit which has an adjustable inductance that depends on the frequency of the energy supplied, which is attached to change f _c can.

Supply lines of various cross-sectional dimensions have previously been used for this purpose, regardless of the shape of the source 16 and. whose control circuit 12 is the function of changing the ultrasonic lines with satisfactory properties 20 frequency f _c in any desired manner in the article »Dispersive Ultrasonic Delay, so that the through the medium 13 all Kom-Lines Using the First Longitudinal Mode in a Strip The components of the signal applied to them, impressed by TR Meeker in the journal IRE Trans-Delay, can be changed. However, as can be seen from actions on Ultrasonic Engineering, Vol. UE-7, No. 2, of FIG. 2, all these components are described in June 1960, pp. 53 to 58. The delay elements are not delayed by the same amount, since the line lines described in this article with the upper frequency components f _c + ω more than Δ have typical delay frequency characteristics, as indicated by point 23 on the statistics. Such a characteristic is shown by curve 21 since the lower frequency component is shown by curve 21 in FIG. nents f _c —ω by a smaller amount than Δ ver

A modulator 15 is superimposed on the baseband signal 30 as delayed by point 26 on the curve

the source of a carrier frequency represented by a 21, and there those in between

Source 16 is from. The frequency of the source 16 is frequencies corresponding to different delays.

determined by the delay control circuit 12, according to the linear part of the delay frequency

that it is equal to the frequency at the im desired characteristic in the frequency band of interest

th point in time the desired delay in the 35 are subject.

Media 13 and 14 is generated. For example, let the output of the delay medium 13 become

taken that the baseband message signal is then applied to a modulator 17 by

Has frequencies up to and including ω and that all components are inversed by a frequency

first delay medium 13 to experience this signal, which is identical to the change in f _c

To delay amountzf. From Fig. 2 it can be seen- 40 measure of the invention is changed. This inversion

Lich that the delay Δ of a frequency f _{c of} the method is such that the signal band in the frequency

Dispersion delay characteristic 21 of the medi spectrum is inverted, so that energy previously

corresponds to around 13. Therefore, the message fre- of the top frequency component of the top

quenz ω superimposed on the frequency f _c , one obtains the sideband has been carried, now in the

at the modulator 15 an output of f _c + w. This 45 lowest frequency component of the lower side

Double sideband signal can appear in the delay band. While there are different ways

device 13, or if there is a bandwidth on which an inversion by a suitable frequency

the signal is large compared to the linear frequency that can be achieved is based on a characteristic of the

Part of the characteristic 21, the invention can be used as a modulator 15 in the simple and effective reproducible

one of the various known single page 50 ways described above. After that there will be a signal

tape types are used, so that its output is always double the f _c , regardless of

is limited to only one sideband, e.g. B. on depending on how f _{c is} changed, namely by

f _c + ω. In either case, the delay can all double the frequency of part of the output

Signal components along the characteristic 21 in the source 16 in a frequency doubler 18. Der

in both directions by changing the frequency f _c ge 55 output of the delay medium 13 is then in

will be changed. a suitable modulator 17 with the doubling

The main applications of the invention include signal 2 f _c mixed, and the lower sideband sen those in which f _c is selected as a function of one of these modulations. Special filter electrical signal of the source 12 is changed. Such arrangements are usually not required, the source 16 can select any of the numerous oscillators 60 to select the lower sideband since the upper sideband has a frequency of 3 f _c ± ω and frequency by voltage , a current or an outside of the sensitivity bandwidth of the ultra-other electrical display, which is the source 16 of the transducer, which is carried to the delay medium 14. So produce z. B. Magnetrons, Klystrons is assigned. The frequency components in the off and similar oscillators frequency excursions, the lower sideband selected 65 are inverted, and depend on the voltage that is applied to certain of them because of the equation
Electrodes is placed. In such an arrangement 2 f _c - (f _c ± ω) = f _c + ω.
The source 12 would supply the variable voltage of this signal to the delay medium 14

which has the same delay frequency characteristic as the medium 13, and since } _c + ω faces exactly the same part of the delay frequency characteristic of the medium 14, as was previously the case for f _c + ω in the medium 13, the average delays are through both media are the same, and each delay can be varied identically depending on changes in frequency / ,,. The effect of the inversion, however, is such that the energy components of the signal 14 in the medium 14 effectively correspond to the dashed curve 22 of FIG. 2, which is a mirror image of curve 21 with respect to the value f _c at any given point in time. By comparing curves 21 and 22 it can be seen that they are complementary to one another in the frequency band of interest. The delay, which is greater than 4 for the upper frequency component in medium 13, as represented by point 23, is compensated for by the delay, which is less than Δ in medium 14, as represented by point 25 . Points 24 and 26 represent the similar compensation for the lower frequency, and compensation for all frequencies within the band occurs so long as f _c and its associated signal sidebands are within the substantially linear range of the delay characteristic. A considerable compensation is still achieved outside the linear part, although it is no longer complete in these areas. Therefore the total delay through both media 13 and 14 is the same for all frequencies and has the numerical value of 2 4.

The message signal obviously leaves the delay medium 14 as a modulation of the Carrier frequency /, .. In the event that this waveform is not suitable for subsequent operations of the System is the desired form, the message or the baseband as drawn, by appropriate Display means are shown, for example by demodulation by means of a conventional baseband detector 19th

The invention has been described in the context of ultrasonic techniques and delay lines, since such devices have essentially a linear delay frequency characteristic and a have a large bandwidth and with this large delays can be achieved. They are easy in construction, more efficient in operation and cheaper to manufacture than equivalent trainings of delay media. It should be noted, however, that the technique of double modulation with a variable Carrier frequency to change the delay also carried out with other delay media can be.

Claims (5)

Patent claims: 1. Electronically variable delay system with a first and a second delay medium, with a first and second modulator for modulating the one to be delayed Signal on a carrier frequency, the first modulator being the first delay medium is connected upstream and the second to the second, with a device for feeding the signal to be delayed to the first modulator, and with a device having an oscillator circuit for supplying a variable carrier frequency to the first modulator, thereby characterized in that the first and second delay media comprising dispersion (13, 14) are practically identical with regard to their dependence of the delay on the frequency are and that the second modulator (17) a Mixer for mixing the output of the first delay medium (13) with a second signal has, the frequency of which is higher than that of the last-mentioned output and is nut the Change in the carrier frequency of the same changes linearly. 2. Delay system according to claim 1, characterized by one of the determination of the carrier frequency (f _c ) serving delay control circuit (12) for changing the resonance frequency of the oscillator circuit of the carrier frequency source (16) with an electrical signal. 3. Delay system according to claim 1 and 2, characterized by a frequency doubler (18) coupled to the second modulator (17) for doubling the carrier frequency (f _c ), 4. Delay system according to one of claims 1 to 3, characterized in that the second modulator (17) means for inverting the signal components of the output of the first delay medium (13). 5. Delay system according to claim 4, characterized in that the second modulator (17) means for applying the lower frequency sideband of its output to the having second delay medium (14). Considered publications: U.S. Patent Nos. 2,629,772, 2,633,492;
"IRE Transactions on Ultrasonic Engineering", Vol. UE-7, No. 2, June 1960, pp. 53 to 58. 1 sheet of drawings 809 518/548 3.68 © Bundesdruckerei Berlin